In recent years occlusive coronary artery disease has been surgically treated with the use of various artery by-pass techniques involving cardiopulmonary by-pass. Although these techniques have been highly successful and can be performed with minimal risk, the unusual surgical skill required, and the complexity of the procedure, limits the operation to a small percentage of those patients who could otherwise be benefited.
In attempts to surgically treat the vast number of coronary artery disease patients to whom the usual open-heart coronary artery by-pass operation was not available or otherwise not indicated, various surgical techniques have heretofore been devised to effect myo-cardial revascularization and neo-vascularization. These procedures can be performed on the beating heart without cardiopulmonary by-pass, thereby greatly simplifying the procedure with an attendant lessening of the risk. These new techniques, moreover, have been greatly advanced by the comparatively recent development of cine-coronary arteriography.
Most promising of the new surgical techniques has been the direct approach to increase the diameter of the coronary arteries narrowed or obstructed by the disease. One technique involves longitudinal incision of the myo-cardial side of the coronary artery at the site of the stenosis or occlusion, with the insertion of a scalpel through a small incision made in the wall of the coronary artery distal to the occlusion. This procedure effects an immediate increase in the size of the lumen for restored blood flow, but in the calcific rigid artery the lumen may remain small. Upon healing, the inside myo-cardial tissue assumes an intima-like surface defining, with the contiguous decompressed arterial zone, a new lumen having an approximately normal diameter. In another of the new surgical techniques, known as percutaneous translumenal coronary angioplasty, an inflatable balloon carried at the end of a catheter or the like is passed through the affected artery to the site of the stenosis as observed in cine-coronary arteriography, and then inflated to compact the stenonic plaque and thereby increase the lumen size by dilation. A distinct advantage of this technique is that the catheter can be inserted through a peripheral artery, thereby obviating surgical opening of the chest wall to expose the heart. This technique, however, has limited application because of major problems in its use in the treatment of stenoses associated with coronary artery rigidity, obstruction, and with single severe and multiple stenoses.
Over the years, the blockage of human arteries has become a leading medical concern. This is so because a variety of serious medical complications may result from arterial blockages that reduce blood flow through an affected artery. More specifically, an arterial blockage may result in damage to the tissue that relies on the artery for its blood supply. For example, if a blockage occurs in an artery leading to the brain, a stroke may result. Similarly, if a blockage occurs in an artery which supplies blood to the heart, a heart attack may result.
Typically, arterial blockages are caused by the build-up of atherosclerotic plaque on the inside wall of the artery. These blockages, which are commonly called stenoses, may result in a partial, or even complete, blockage of the artery. As a result of the dangers associated with these arterial blockages, a variety of procedures have been developed to treat them. An angioplasty procedure is, perhaps, the most commonly used procedure for such treatment. An angioplasty procedure involves the use of an inflatable angioplasty balloon to dilate the blocked artery. A typical inflatable angioplasty device, for example, is disclosed in U.S. Pat. No. 4,896,669 which issued to Bhate et al. The Bhate et al. angioplasty device includes an inflatable angioplasty balloon which is insertable into a peripheral artery of a patient for positioning across a stenosis. Once positioned, the angioplasty balloon is then inflated to dilate the stenosis within the artery thereby improving the blood flow through the artery.
While angioplasty balloons have been widely accepted for the treatment of stenoses, recent studies have indicated that the efficacy of the dilation of a stenosis is enhanced by first, or simultaneously, incising the material that is creating the stenosis. Not surprisingly then, angioplasty balloons have been equipped with cutting edges, or atherotomes. These cutting edges are intended to incise the stenosis during the angioplasty procedure to facilitate dilation of the stenosis.
An example of an angioplasty balloon equipped with cutting edges is disclosed in U.S. Pat. No. 5,196,024 which issued to Barath for invention entitled “BALLOON CATHETER WITH CUTTING EDGE.” The Barath device includes an inflatable angioplasty balloon with a number of atherotomes mounted longitudinally on its surface. During the inflation of the Barath balloon, the atherotomes induce a series of longitudinal cuts into the stenotic material as the balloon expands to dilate the stenosis. As a result of such longitudinal cuts, the stenosis is more easily dilated, and the likelihood of damaging the artery during dilation is significantly reduced.
In general, the use of angioplasty has been found to be an effective means for reducing arterial blockage associated with the buildup of atherosclerotic plaque. In some cases, however, it has been found that the atherosclerotic plaque which forms a particular stenotic segment may be too rigid to be effectively dilated. In such cases, traditional angioplasty techniques have been found to be largely ineffective and, in some cases, even harmful. As a result, a number of differing techniques have been developed for the treatment of hardened, or rigid stenotic segments.
One such technique, which is specifically targeted at the coronary arteries, is transection. Transection, as applied to the coronary arteries, involves the creation of an elongated incision within the artery where the targeted stenosis is located. More specifically, a longitudinally oriented incision is created which spans the targeted stenosis and is positioned along the wall of the artery which is closest to the cardiac muscle. Creation of the incision causes the formation of a new arterial segment, with the new segment being composed partially of the previously occluded artery, and partially of the heart muscle, or myocardium. The new arterial segment is created from the natural healing process that to create a coronary-myocardial artery. Effectively then, transection overcomes the occluding effect of atherosclerotic plaque by allowing the occluded artery to expand into the heart muscle or myocardium. A description of this procedure is provided in “Coronary Artery Incision and Dilation” Archives of Surgery, December 1980, Volume 115, Pages 1478-1480, by Banning Gray Lary, M.D.
For the transection procedure to succeed, it is important that the incision be made on the portion of the coronary artery which directly faces the heart muscle. This is so because the transection procedure involves cutting through the arterial wall, a procedure which would ordinarily result in an uncontrolled blood loss and, perhaps, the death of the patient. However, if the transection is made on the portion of the artery against the heart, the epicardial tissues which cover the heart and the coronary arteries prevent the loss of blood, allowing the new artery to form.
Unfortunately, in the context of a transection procedure, currently available angioplasty balloons have a particular disadvantage. More specifically, practice has shown that it is generally difficult to direct the atherotomes of a traditional angioplasty balloon with the accuracy required for a successful transection. Instead, when a traditional angioplasty balloon is employed, there is an ever present danger that the transection will be created in a part of the arterial wall that is not adjacent to the heart. Specifically, there is a present inability to precisely control the position an angioplasty balloon and cutting edge in both a longitudinal and a rotational direction.
Another disadvantage associated with the use of traditional angioplasty balloons for the creation of coronary transections involves the depth of the created incision. More specifically, practice has demonstrated that effective transection requires that the created incision be deep enough to allow the new artery to form.
Another problem associated with traditional balloon angioplasty is that when inflated, perfusion is interrupted. This limits the time during which the incision may be made.